1. Field of the Invention
The present invention relates to a digital clipping circuit, and, in particular, to a video signal clipping circuit used, for example, in a digital video tape recorder (hereinafter, referred to as "digital VTR").
2. Description of the Related Art
Recently, a digital recording system, which eliminates drawbacks of an analog recording system and achieves high image quality, has been employed in a conventional video tape recorder. A video tape recorder employing such a system is called a digital VTR. A signal processing circuit used in the digital VTR comprises a Y-C separation circuit for obtaining a luminance signal (Y signal) and a chrominance signal (C signal) from an NTSC signal, a pre-emphasis circuit for pre-emphasizing the luminance signal, and a digital clipping circuit for clipping a spike produced by the pre-emphasis at a predetermined level.
One example of a conventional digital clipping circuit comprises a comparator for comparing an input signal and a reference signal (clip level signal), and a switching circuit for selecting one of the input signal and the reference signal. When the level of the input signal is above the clip level, the input signal is clipped at the clip level and the clipped signal is output from the switching circuit. When the level of the input signal is equal to or lower than a clip level, the input signal is output from the switching circuit with no level changes. The clipped signal loses a soft-clip characteristic (or a rounded portion) and has a so-called hard-clip waveform. Thus, in the conventional digital clipping technique, the output signal is degraded.
There has been a great demand for a digital clipping circuit having a soft-clip characteristic, to prevent degradation of an output signal.